A DUP MP has hit back after an official complaint was made about him to the Parliamentary watchdog for using House of Commons notepaper to promote food banks.

South Antrim representative Paul Girvan explained on Twitter he had sent out 234 letters to local businesses encouraging them to support two food banks in his constituency.

He said one recipient "took umbridge" that the letter was written on official stationery and reported him to the Parliamentary Standards Commissioner.

The complainant is the owner of a Co Antrim business park.

Mr Girvan now faces an investigation for a breach of the code of conduct for MPs.

The regulations state that "Members shall ensure that their use of public resources is always in support of their parliamentary duties".

The MP said he was "fully cooperating" with the commissioner for the inquiry.

"I was only trying to help two local charities, but I'm confident I'll beat this process," Mr Girvan said.

"MPs were engaged in a similar process to help Syrian refugees last year and quite a number engaged in doing this through posting letters rather than email.

"We've been engaged in food banks for a number of years. We felt it was a lot to keep asking a small number of businesses to keep contributing so we decided to widen the circle for them."

Mr Girvan said he was "taken aback" by the complaint, adding: "I was trying to do something good and that was being used as an opportunity to raise an inquiry for no benefit."

The complaint from the businessman, which has been seen by the Belfast Telegraph, said he had received six copies of the letter "on House of Commons notepaper" along with a "private circular for coffee mornings".

Addressing the Parliamentary Commissioner for Standards, he said: "I believe it is incorrect for an MP to use House of Commons notepaper for personal and private matters, also to further use pre-paid House of Commons envelopes for private usage.

"I believe each of these items should be paid for personally by the MP concerned."

He also alleged: "I can only guess the MP has used a commercial directory, circulating thousands of individuals, professionals, businesses and organisations."

Mr Girvan said he believed the complainant may have received the six copies in error as he had multiple tenants in his business park.

Regarding the response to his letter campaign, Mr Girvan also commented on his Twitter account: "I am hugely encouraged by the South Antrim response to the Christmas appeal so far.

"There is still time for others to support the Newtownabbey Foodbank and Oasis Caring in Action during this season of giving and goodwill."

Earlier this month a senior Labour MP apologised and repaid the minor sum of £2.97 for another stationery-related transgression.

Dame Margaret Hodge, a former chair of the Public Accounts Committee, used parliamentary stationery and phones to carry out work for an independent review of London's proposed Garden Bridge for Mayor Sadiq Khan.

Mr Girvan is not the only DUP MP being investigated by the Parliamentary Standards Commissioner.

In September Ian Paisley referred himself to the watchdog over claims in a newspaper that he failed to declare hospitality worth £100,000 from the Sri Lankan Government in 2013.

He strongly denied the allegations, insisting they were "defamatory" and "devoid of fact or logic".